The applicant proposes to develop a highly sensitive imaging plate based on ET phosphors and read-out system for in vivo and in vitro autoradiography. It is expected that the plates will have the capability of recording images produced by beta particle emission from (3)H, (125)I and (14)C, the principal radioactive tags employed in brain and whole body imaging. It is expected that, in contrast to X-ray film, at least a 10-fold increase in sensitivity will be achieved, there will be a dynamic range in excess of four orders of magnitude, the response will be linear over this range, and the plates will be reusable and will have a tailorable resolution capability. During Phase I, imaging plates will be fabricated, imaging characteristics will be measured employing (3)H, (125)I and (14)C standards, and read-out systems will be evaluated for obtaining the best quality images. Given the speed-up of experimentation expected and the potential for superior images, the applicant claims that such imaging plates can be expected to replace X-ray film in autoradiography applications.